Nestable fabricated thermoplastic container

ABSTRACT

A fabricated cup or other nestable container in which the sidewall is formed from a rectangular sheet-like blank of a thermoplastic material, particularly an expanded thermoplastic material, the blank having its ends joined to one another in a liquid-tight seam extending the full height thereof to form a sleeve, the blank having a relatively high degree of orientation or heat-shrinkability extending circumferentially of the sleeve, the fabrication of the sidewall from the sleeve being accomplished by telescoping the sleeve over a generally frusto-conically shaped mandrel, by exposing the sleeve to heat to cause it shrink to conform to the configuration of the mandrel and by stripping the shrunken sleeve from the mandrel. A two-piece container may also be formed from such a sidewall by affixing an end closure element to the bottom or smaller end of the sidewall. A one-piece container may also be formed in this manner by using a blank of sufficient height so that a substantial portion of the sleeve formed therefrom extends beyond the smaller end of the forming mandrel, such substantial portion, when the sleeve is exposed to heat, being shrinkable to form an annular planar portion disposed transversely of the longitudinal axis of the mandrel and a relatively small tubulation which extends longitudinally from the interior of the annular planar portion and which, by the application of pressure thereto while at elevated temperature, may be caused to collapse and fuse together to close the bottom of the container in a liquid-tight manner. A container of this type may be used to advantage to contain any liquid or other fluent product therein in face to face contact with the interior surface of the sidewall thereof, and when the container is fabricated from an expanded material, because of the insulating characteristics of such material, a container fabricated therefrom may be used to particular advantage as a handholdable cup for coffee or other hot beverage.

This is a division of application Ser. No. 211,259, filed Dec. 31, 1971.now U.S. Pat. No. 2,854,583.

GENERAL DESCRIPTION OF THE INVENTION

It has long been recognized that drinking cups and other nestablecontainers with superior properties, especially for the retention of hotbeverages such as coffee, can be formed from expanded thermoplasticmaterials, the most popular of which has proven to be expandedpolystyrene. A very popular cup of this type is a one-piece cup which ismolded directly from expandable polystyrene beads in a steam chest.However, in forming cups in this manner, it has proven to be necessary,for purposes of imparting adequate strength, rigidity and liquidimpermeability to the sidewall theoref, to construct such cups with athick sidewall, at least in relationship to the sidewall thickness ofother types of insulated cups. As a consequence of this added sidewallthickness, it is not possible to obtain as small a stacking height, orspacing, between like cups in a nested stack thereof, with the resultthat such cups require considerably more storage space than a comparablequantity of other types of nestable insulated cups. Another disadvantageof the so called steam chest molded cup is that, as an inherentconsequence of its mode of manufacture, the external surface of itssidewall can only be decorated by post decorating or printing techniqueswhich are slower and more expensive that the flexographic and othersheet printing techniques which may be used in decorating cupsfabricated from pre-printed sheet. As a result, the vast majority ofsuch steam chest molded cups which appear in the market place do notcontain a decorated or printed outer surface.

Another known type of insulated or expanded thermoplastic drinking cupwhich has enjoyed some measure of commercial popularity is a two-piececup such as that which is manufactured and marketed by the assignee ofthis application under the trademark "X-Fome" and which corresponds tothe cup described in U.S. Pat. No. 3,468,467 which is assigned to theassignee of this application. The sidewall of such cup may be formed byconventional cup fabricating techniques from a crescent-shaped blank ofan expanded plastic material, which, in turn, is cut from a pre-printedsheet or web of indefinite length thereof. By controlling the density ofsuch sheet, it is possible to fabricate a cup with adequate strength,rigidity and liquid impermeability and which, nonetheless, has aconsiderably thinner sidewall than a steam chest molded cup for superiorstacking or nesting properties in relationship thereto. Also, the easewith which the exterior of the sidewall of such cups can be providedwith attractive decoration by pre-decorating the sheet from which thesidewall blanks are formed, has made it possible for a substantialportion of such cups to be decorated in a way which has proven to bequite popular in the trade. One of the drawbacks of such a cup is itscostliness, at least insofar as material costs are concerned, inrelationship to the steam chest molded cup, due in part to the scrapwhich is inherently formed when a crescent shaped sidewall blank is cutfrom a sheet or web of normal character.

Yet another known type of insulated or expanded thermoplastic drinkingcup which has also enjoyed some measure of commercial popularity is aone-piece, seamless deep drawn cup which is manufactured and marketed bythe assignee of this application under the designation VP-7 and whichcorresponds to the cup described in co-pending U.S. patent applicationSer. No. 555,922 (J. R. Tiffin et al.), now U.S. Pat. No. 3,666,162.Such cups can, in somewhat higher densitites than conventional steamchest molded cups, be formed to very close manufacturing tolerances andwith very low stacking height, and because of these features, they have,in spite of somewhat more costliness than the steam chest molded cup andthe two-piece cup described above, and in spite of the fact that theycan only be decorated after forming, gained a substantial measure ofpopularity in the coin-operated beverage vending machine market.

As can be seen from the foregoing discussion, each of known types ofinsulated cups referred to therein has certain advantages which makes itwell-suited for some uses, and certain limitation which makes itless-suited than one of the other types for other uses. In accordancewith the present invention, however, there is provided an insulated cupwhich combines a wide range of desirable properties, without offsettinglimitations, and which is, therefore, well-suited for a wide range ofapplications for insulated cup. The sidewall of such cup can be formedfrom rectangular blanks, and therefore without the scrap and inherentexpense involved in the severing of crescent-shaped sidewall blanks froma parent sheet or web, and the sidewall of such a cup may be relativelyinexpensively provided with attractive, high quality decorativematerial. Additionally, such cup may be provided with relatively goodstacking or nesting characteristics, and with close manufacturingtolerances to provide the reliable denesting which is important incoin-operated vending machine utilization of cups. Relativelyinexpensive high quality cups according to the present invention mayreadily be formed on a high production basis in either a one-pieceversion or a two-piece version.

The sidewall of either such version is formed from a web of polystyreneor other thermoplastic polymeric sheet material which has a substantialdegree of orientation or heat-shrinkability in the machine direction, bysevering rectangular sidewall blanks from such web, preferably afterprinting or other decorative material is applied to the web byflexographic or similar printing technique in a repeat pattern inregistration with the blanks to be cut therefrom, by forming acylindrical sleeve from each such blank with the machine direction ofthe parent web extending circumferentially thereof, including theforming of a liquid tight lapped seam between the ends of the sleeve, asby heat sealing, by placing the sleeve over a forming mandrel having anouter forming surface corresponding to the desired configuration of theinner surface of the sidewall of the nestable cup to be formedtherefrom, by heating the sleeve while it is so positioned over themandrel to cause it to heat shrink into conforming face to face contactwith the forming surface of the mandrel, and by stripping the shrunkensleeve from the mandrel. A separate bottom closure may be affixed to asidewall formed in this manner either while the sleeve is still inposition on the mandrel, or after it is removed, by any of several knowncup-manufacturing techniques. Alternatively, a one-piece cup may beformed by starting with a sleeve which is highly oriented in thecircumferential direction and which exceeds the height of the formingmandrel over which it is to be telescoped by a distance of the order ofone-half of the smaller diameter of such mandrel, with the sleeve beingso telescoped over the mandrel that the excess portion of the sleeveextends beyond the smaller end of the mandrel. When such a sleeve isexposed to heat, the excess portion thereof will shrink to form aannular planar portion extending inwardly across the smaller end of themandrel and a relatively small diameter tubulation extendinglongitudinally from the interior of such planar portion. By theapplication of opposed compressive forces to such tubulation while it isat elevated temperature, it can be caused to collapse and to fusetogether to close the interior of the annular planar portion in aliquid-tight fashion.

The fabrication of either a two-piece cup or a one-piece cup accordingto the present invention is effective to provide a cup whose sidewallthickness increases from a lesser thickness at the location of greatestdiameter to a greater thickness at a location of lesser diameter. Thisis especially desirable in that it provides adequate thickness in thelower portion of the cup to protect the hand of a user from thetemperature of a hot beverage therein, while keeping the wall thin atthe top of the container so that the bead or rim which is normallyformed therein need not be excessively thick. Also, the degree of taperin the sidewall can readily be increased in the lower thicker regions tooffset the adverse effect of a thicker sidewall on the stacking ornesting characteristics of like cups of this type.

Accordingly, it is an object of the present invention to provide animproved nestable cup or similar container in which the sidewall isfabricated from a sheet of thermoplastic material.

More particularly, it is an object of the present invention to providean improved nestable cup at least the sidewall of which is fabricatedfrom a sheet of expanded thermoplastic material to reduce the weight andcost thereof and to improve the insulating properties thereof.

More particularly, it is an object of the present invention to provide anestable cup or similar container at least the sidewall portion of whichcan be fabricated from a rectangular blank of heat-shrinkablethermoplastic material.

More particularly, it is an object of the present invention to providean insulated nestable cup or similar container at least the sidewallportion of which can be fabricated from a rectangular blank of expandedheat-shrinkable thermoplastic material.

More particularly, it is an object of the present invention to providean insulated nestable cup or similar container which has a relativelythin wall for good stacking characteristics and which can be fabricatedfrom a pre-printed blank of expanded thermoplastic material so that theexternl surface of the sidewall of such cup or container carriesattractive decorative material.

It is further object of the present invention to provide an insulatednestable cup or similar container in which the thickness of the sidewallthereof varies from a lesser thickness at an upper, larger portion to agreater thickness at a lower, smaller portion, and it is a corollaryobject to provide such a cup or container with a sidewall taper thatvaries from a lesser taper at the upper, larger portion to a greatertaper at the lower, smaller portion.

It is a further object of the present invention to provide a novelmethod of fabricating the sidewall of an insulated nestable cup orsimilar container.

It is also an object of the present invention to provide a method forthermally fabricating the sidewall of a nestable cup or similarcontainer from a rectangular blank of thermoplastic material and withoutthe need for wasting a portion of the material in such blank, and, moreparticularly, it is an object of the present invention to provide amethod for thermally fabricating the sidewall of such a cup or containerfrom a rectangular blank of an expanded thermoplastic material to impartgood insulating properties to such sidewall.

More particularly, it is an object of the present invention to providemethods of producing one-piece and two-piece externally decoratedinsulated cups wih good stacking characteristics and on an economicalbasis.

For a further understanding of the present invention and the objectsthereof, attention is directed to the drawing, the following descriptionthereof, the detailed description of the invention and the appendedclaims.

DESCRIPTION OF THE DRAWING

FIG. 1 is an elevation view, partly in section, of a nestable insulatedcontainer in accordance with the present invention;

FIG. 2 is a fragmentary sectional view, at an enlarged scale, of a cupin accordance with FIG. 1, showing a like cup in phantom to illustratethe stacking relationship therebetween;

FIG. 3 is a plan view of a rectangular blank from which a cup of thetype shown in FIG. 1 can be fabricated;

FIGS. 4-8 are schematic views illustrating sequential steps in thefabricating of a two-piece container of the type shown in FIG. 1 from ablank of the type shown in FIG. 3; and

FIGS. 9 and 10 are schematic views illustrating sequential steps in thefabricating of a one-piece container.

DETAILED DESCRIPTION OF THE INVENTION

While nestable insulated cups in accordance with the present inventioncan be constructed in a wide variety of configurations, the presentlypreferred embodiment of such cup, as is shown generally by referencecharacter 11 in FIGS. 1 and 2, comprises a two-piece cup. Cup 11 isformed, as will be hereinafter described more fully, by heat shrinkingan open-ended cylindrical sleeve about a forming mandrel which has anouter forming surface corresponding to the desired contour of the insidesurface of the sidewall of the cup, the sleeve having a relatively highdegree of orientation in the direction extending circumferentiallythereof. Such a sleeve is formed, in accordance with the preferredembodiment of the method of the present invention and as will behereinafter described more fully, by heat sealing or otherwise joiningthe opposed lapped ends of a rectangular blank of suitable material in avertically extending liquid tight seam, and as a consequence of suchmethod of forming, cup 11 will have a visible, vertically extending sideseam 12 in the sidewall of the cup, which sidewall is identified byreference character 13.

Sidewall 13 of cup 11 has a major uninterrupted portion 13a, shown asextending from the top of the cup to an inwardly extending stackingshoulder 14 which is located near the bottom of the cup, and which isprovided to receive the botttom of a like cup inserted therein toprovide a positive minimum spacing between nested or stacked cups, as isshown in FIG. 2 and as is well understood in the art. Of course, as isalso well understood in the art, equivalent stacking means could beprovided in the sidewall of the cup at a relatively higher elevation inthe sidewall, in which case the major portion of the sidewall would belocated below the stacking means. In either such event, because of theheat shrinking step involved in the manufacture thereof, the thicknessof the sidewall of the container decreases as the diameter of the cupincreases, and adequate thickness may be provided in the region of thesidewall which is normally grasped by the hand of a user to protect orinsulate the hand from the heat of a hot beverage such as coffee. At thesame time, it is possible to maintain the thickness in the region of thetop of the cup at a low enough value to form a thin tight bead, shown as15 in FIG. 1, surrounding the mouth of the container. Because closenesting of the like cups is adversely affected by increased wallthickness, the major portion 13a of the sidewall of cup 11 is shown asincreasing in taper, as measured by the included acute angle between thelongitudinal central axis of the cup and a line tangent to the sidewallthereof, as the cup diameter decreases and the wall thickness increases,it being noted that increasing wall taper improves close nesting, as isunderstood in the art.

The bottom or smaller end of cup 11 is shown as being closed by agenerally horizontally extending bottom member 16 which is joined to asidewall portion 13 in a liquid-tight fashion. In the illustratedembodiment, such bottom member is formed from a disc-like element of athermoplastic material sealable to and compatible with the material ofthe sidewall, e.g. the same material as the sidewall. This bottom memberis joined in a liquid-tight fashion to an inturned portion of thesidewall of the cup, as by heat-sealing or with an adhesive, ashereinafter described. However, it is also contemplated that such bottommember may be formed integrally with the sidewall of the cup, as is alsohereinafter described.

The sleeve from which a cup of the type shown in FIG. 1 may be formed,which is designated by numeral 17 in FIG. 6, is formed from arectangular sheet or blank of an expanded plastic material, such asexpanded polystyrene, such blank being designated by numeral 18 in FIG.3. The blank is formed by severing from a parent web or sheet ofappropriate material, preferably a web of indefinite length of suchmaterial which is highly mono-axially oriented in the longitudinaldirection. Such a web may be produced, in turn, by slitting a seamlessextruded tube of appropriate thermoplastic material along one or morelongitudinally extending lines which, if there are more than one, extendparallel to one another. The requisite orientation in the machinedirection may readily be imparted to such web, or webs, by engaging theextruded tube while it is at a suitable orientation temperature betweenopposed counterrotating rolls which are driven at peripheral speedssubstantially in excess of the lineal speed of the thermoplasticmaterial leaving the extruder, all as is well understood in the art.

In practice, it is normally desired that blank 17 be provided withprinting or other decorative material on the surface which is destinedto be the outer surface of the finished cup. For simplicity, decorativematerial is shown only in FIG. 3 where it is identified by referencecharacter 19, it being understood that it will also be present in otherviews of the blank, or of the sleeve or cup which are sequentiallyformed therefrom.

This decorative material may be rapidly and relatively inexpensivelyapplied, in multiple colors if desired, by applying it in a repeatpattern to the parent web before the individual blanks are severedtherefrom, as by means of known printing devices such as a flexographicprinting press or an offset rotary letter press, all as is wellunderstood in the art. It is to be noted that, because of thedifferential contraction of the material involved in shrinking acylindrical sleeve into the form of the sidewall of a nestable cup, theprinting should be applied to the web in a form which is distorted fromits desired form, so that upon such differential contraction, theprinting will change in form into its desired form.

The fabrication of sleeves such as that identified by numeral 17 in FIG.6 from blanks such as that identified by numeral 18 in FIG. 3 isillustrated in FIGS. 4 and 5. Individual blanks 18 are fed to a rotarymandrel head 31. Mandrel 31 is mounted on shaft 32 and held by collar 33and set screw 34. Shaft 32 is rotated under power. The blank 18 is heldto the mandrel by the vertical row of vacuum ports 35 connected tovertical passage 36 and through radial port 37 into the hollow centerpassage of shaft 32. The mandrel 31 is concentric with a stripper sleeve38 carried on a bracket and vertical spindle 39 (FIG. 5). Blank 18 isattached at the leading edge 21 to mandrel 31 by vacuum, and as themandrel rotates, blank 18 is wrapped around the surface of the cylinder,which is the outer surface of the mandrel 31 to form sleeve 17. Thestripper sleeve 38 is in its lowered position out of interference withsleeve 17. The mandrel is the desired size (diameter) in relation to thecup forming mandrel that is to receive the sleeve when finished, ashereinafter described.

As the mandrel 31 completes a revolution, the trailing edge of the blankoverlaps the leading edge to form a lap seam for the cylinder. The seamis made by heat and some pressure in bonding the overlapped regions ofplastic together, in a liquid-tight seam extending the full height ofthe sleeve accomplished by bringing heater 40 into contact with theseoverlapped areas of the sleeve 17. Heater 40 has a surface layer 40a ofTeflon material to prevent sticking of the heater nose on the sleeve.Heater 40 is pressed against the overlapped plastic sheet and thecombined heat and pressure of heater 40 irons the lap seam intosubstantially less than the double thickness of the overlap. This formsa feathered edge compatable with the thickness of the remainder ofsleeve 17. Heater 40 is on an appropriate carriage to be brought intoand out of contact with the sleeve at the proper time and rotation ofmandrel 31 during pressure contact of heater 40 as it irons the seam ofsleeve 17.

As an alternative, the lap-seam may be made with a hot melt adhesiveapplied to the inner surface of the blank 18, such as in the areabetween edge 20 (FIG. 5) and phantom line A. Heater 40 will activate theadhesive area and form an adhesive bond between the overlapped ends ofthe material on mandrel 31.

To fabricate a two-piece cup from a sleeve 17, produced as hasheretofore been described, there is provided a forming mandrel showngenerally at 41 in FIG. 6. Mandrel 41 has an exterior surface 41a whichis contoured to correspond to the desired contour of the interiorsurface of the cup 11 which is to be formed therefrom, or at least thesidewall portion, and the mandrel is suspended from a support member 42.A sleeve 17 which is to be formed on mandrel 41 is telescoped thereoverwith the upper end of sleeve 17 being held in a position aligned withthe maximum dimension of forming surface 41a by means of an expansibleclamping ring 43. Clamping ring 43 comprises a series of arcuate sleevecontacting segments extending inwardly from an O-shaped spring, andclearance is provided between the clamping ring and the surroundingstructure to provide for radial expansion of the sleeve to accommodatethe insertion of the end of a sleeve between the inner ends of suchsegments and the terminal portion of the forming surface 41a of mandrel41. Clamping ring 43 is retained in a fixed position relative to theaxis of mandrel 41 in a cavity 48 of support member, to the bottom ofwhich is attached a removable flange 49 on which clamping ring 43slidably rests.

As is shown in FIG. 7, when sleeve 17 is positioned over the formingsurface 41a of mandrel 41, the so positioned elements are exposed to asource of heat, as by advancing them in unison into a region, exposed toinfra-red heating elements 51,52 and 53, elements 51 and 52 beingdirected against opposed sides of mandrel 41 and element 53 beingdirected against the bottom thereof. For purposes of illustration,elements 51-55 may be considered to be electric elements of the typemanufactured by Irex Corporation of Riverdale, New Jersey and sold asRadplane radiant process heaters. As an alternative to heating by way ofinfra-red elements, it is also contemplated that the so positionedsleeve and mandrel could be heated by advancing them through a tunnelthrough which heated air is circulated. However, infra-red heating hasbeen found to be more controllable and, because of the penetrativeeffect of the infra-red radiation, somewhat faster than forcedconvection heating. In any event, the application of heat will cause theportion 17a of sleeve 17 which overlies the side portion of the surface41a to shrink into tight conforming relationship therewith.

To avoid chilling of the interior surface of the sleeve during shrinkingwhich would, of course, inhibit shrinking, it has been found desirablethat the mandrel be at an elevated temperature during the shrinkingstep, but not at a temperature higher than the softening point of thethermoplastic material from which the sleeve is formed. With sleevesformed from expanded polystyrene, good results have been obtained with amandrel pre-heated to a temperature of the order of 150° F.

Prior to the exposure of sleeve 17 to the heating effect of heatingelements 51,52 and 53, a disc shaped element of thermoplastic material71, from which bottom element 16 of the finished cup is to be formed, isbrought into position against the bottom of mandrel 41 in coaxialrelationship to sleeve 17. Element 16 is retained in such positionduring the heating step by vacuum applied thereagainst through acircumferential series of ports 44 which are in fluid communication withvacuum line passages 45 and 46 extending through a central spindleportion 47 of mandrel 41 and, in turn, communicating with a vacuumsource, not shown, external to the mandrel. The use of a pair of suchvacuum line passages, 45 and 46, makes it possible to maintain a vacuumin the annular space defined by the outer surface 41a of mandrel 41 andthe central spindle 47 thereof. While such vacuum is not utilized in theillustrated embodiment of the invention, it can be utilized to advantageby providing vacuum ports through the surface 41a to help in the formingof sharp corners in an upper portion of the finished cup, as in the caseof a cup having a stacking rim in an upper portion thereof or a cupformed from very thin and/or very low density material and therebyrequiring a circumferentially extending stiffening rib near the upperportion thereof.

While the portion of sleeve 17 which overlies the side portion of thesurface 41a of mandrel has shrunk into conformity therewith, asheretofore explained, the terminal portion of sleeve 17 which extendsbeyond the smaller end of the mandrel 41 will continue to shrink to forman annular, generally planar portion 17b which is integral with, andextends inwardly from the smaller end of portion 17a, and which overlapsthe marginal portion of element 71 in a continuous, circumferentialpattern. In the meanwhile, the interior portion of element 71 willpermanently shape itself to conform to the concave curvature of thebottom of mandrel 41 by the effect of the heat and vacuum forces towhich it is exposed, some vacuum naturally bleeding from ports 44 intothe region above the interior portion of element 71. After the shrinkingoperation, the mandrel 41 with the shrunken sleeve 17 and the shapedbottom element 71 thereon is removed from exposure to heating elements51, 52 and 53 and, as is shown in FIG. 8, a heated sealing tool 61, witha non-stick contact surface layer 61a such as a woven glass fabric, forexample, of the type sold under the designation Flour glass, which isimpregnated with Teflon resin or other non-stick material, is broughtinto pressing contact therewith to form a continuous, circumferentiallyextending, liquid tight heat seal between portion 17b of sleeve 17 andthe underlying marginal portion of element 71.

After the seal has been effected between portion 17b of sleeve 17 andthe underlying portion of element 71, as has been described, theshrunken sleeve is stripped from the mandrel and is further processed ina conventional manner, for example, by rolling the rim 15 therein bymeans of conventional rim forming devices, by inspecting finished cupsand by collecting and packaging a multiplicity of like cups in nestedrelationship with one another.

A cup of the type shown in FIGS. 1 and 2 may also be formed of one-piececonstruction, as well as of two-piece construction as heretoforedescribed. Such a cup may be constructed, as is shown in FIGS. 9 and 10,from a sleeve 117 which is the same as sleeve 17 except that it islonger and has a relatively long portion adapted to extend beyond thesmaller end of the forming mandrel, which may be considered to theforming mandrel depicted in FIGS. 6-8. In such a case the startingsleeve from which the cup is to be formed is of sufficient length tohave a substantial portion which extends beyond the smaller end of themandrel 41 when the upper edge of such sleeve is in its aligned positionwith the upper portion of the forming surface of the mandrel. Upon theheat-shrinking of such a sleeve, as is shown in FIG. 9, will form amember with a sidewall portion 117a, a generally planar annular portion117b integral with portion 117a and extending radially inwardly from thelowermost edge thereof, and a relatively small tubulation 117c whichextends longitudinally from the interior edge of the planar portion 117band which is integral with sidewall portion 117a and annular portion117b. The bottom of a cup may be formed in the shrunken member 117,preferably while such member is still on the mandrel, by the applicationof heat and pressure to the bottom of such member to cause thetubulation to 117c to collapse and fuse together with planar portion117b. This may be done by means of a pressing and shaping tool 161 whichhas a contoured surface adapted to contact the bottom of the shrunkensleeve and to shape it to the desired final configuration. Tool 161 isnormally in a non-contacting position relative to mandrel 41, as isshown in FIG. 9, and it may be urged from such position into the sealingand pressing position depicted in FIG. 10 by the action of a spring 162.As the shrunken sleeve 117 on mandrel 41 may not be at a sufficientlyhigh temperature at the time that tool 161 is brought into contacttherewith to permit the sealing and pressing operation to be performedwithout additional heat, tool 161 may be considered to be heated bymeans, not shown, and to have its contact surface covered with amaterial 161a of the type used in regard to the contact surface 61a ofthe tool 61 of FIG. 8, as heretofore described. In case that the bottomsealing step in the manufacture of either the two-piece cup, as is shownin FIG. 8, or of the one-piece cup, as is shown in FIGS. 9 and 10, isdone while the shrunken sleeve elements are at a sufficiently hightemperature to obviate the need for additional means to heat theapplicable sealing tool, an unheated sealing tool may be used, in whichcase it will normally be unnecessary to coat the contact surfaces of thesealing tools with the special non-stick material of surfaces 61a or161a, as the case may be.

In general, it is recommended, for good stacking characteristics, thatthe sidewall taper of cups or other nestable container constructed inaccordance with the present invention increase from a taper of the orderof 5° - 7° at the top thereof to a taper of the order of at least 15° atthe bottom thereof. To obtain a good balance between performance andcost, for a cup of the order of size of a single serving of coffee orother hot beverage and based on current economic conditions, a startingor parent sheet of expanded polystyrene of a thickness of the order of20 to 30 mils of a density of the order of 10 to 18 pounds per cubicfoot, and with an orientation in the longer or machine direction of theorder of 75% and an orientation in the shorter or cross direction of theorder of 15% is preferred with sheets of a density of the order of 10pounds per cubic foot and a thickness of the order of 25 mils (0.025in.) being highly satisfactory for the fabrication of single serving hotdrink cups. However, while heat-shrinkable, expanded polystyrene iscurrently the preferred material for the fabrication of insulated cupsand other nestable containers according to the present invention, suchpreference is based mainly on the cost of polystyrene relative to otherthermoplastic resins. Such cost relationships could change with thepassage of time, and it is therefore to be noted that otherheat-shrinkable, expanded thermoplastic materials can, from a technicalpoint of view, be employed in the practice of the invention, includingsuch materials as polypropylene, polyethelyne and polyvinyl chloride. Itis also to be noted that cups constructed in accordance with the presentinvention can be used as cold drink cups, where the insulatingproperties would not be as important, but would still be of value inpreventing moisture from condensing on the outer surfaces. In the caseof cups or other containers designed for holding cold drinks or forother fluent products at ambient temperature, the use of an expandedthermoplastic material would offer potential benefits, in relation tonon-expanded materials, chiefly in reduced material costs.

While the invention has been described with respect to a nestablecontainer which is circular in cross-section at all elevations, it is tobe noted that other configurations can be provided to suit the wishes ofthe designer. For example, a nestable container which has thecross-section of a round-cornered square at all elevations can beprovided, and a nestable container which has a circular cross-section atthe top gradually merging into the cross-section of a round-corneredsquare at the bottom can be provided. Also, where close nesting is notrequired, an attractive nestable container with a sidewall having areverse curvature, similar to the popular "Coke" tumbler, can beprovided. Containers which are non-symmetrical can also be provided.

It is also to be noted that the present invention can be practiced withnon-expanded, heat-shrinkable thermoplastic materials in cases where thenestable cups or other containers do not require thermal insulatingcharacteristics. Such containers would still have advantages overcontainers formed from such materials by vacuum forming or other sheetdrawing techniques, in regard to the ease and relatively low cost withwhich the sidewall thereof could be decorated. Also, by virtue of themode of manufacture thereof, such containers, being fabricated fromrectangular blanks, would involve a considerably lower amount of scrapto be reground and recycled, and would inherently avoid the problem ofexcessive thinning in the sidewall region near the bottom which ischaracteristic of such containers when formed by any such popular sheetdrawing technique and which, in regard to relatively tall, narrowcontainers, can lead to a significant reduction in the strength in thebottom regions of the sidewalls of such containers.

It is thought that the invention may be better understood from thefollowing example, which is not to be construed as limiting the scope ofthe invention in any way.

EXAMPLE

The sidewalls of two-piece cups of the outline of that shown in FIG. 1were constructed from pre-printed rectangular blanks of 10 lbs. per cu.ft. density polystyrene, 93/8 in. long by 4 in. wide by 25 mil (0.025in.) thick, such blank having 75% orientation in the longer or machinedirection and 15% orientation in the shorter or cross direction. Thebottom elements were fabricated from polystyrene sheeting of the samespecifications. Each finished cup had an overall height of 3.448 in.,and I.D. at the rim of 2.920 in. and I.D. inside of the stackingshoulder of 1.892 in., wall thickness, at the rim, of 30 mils. a wallthickness, immediately above the stacking shoulder, in excess of 40mils, a curved sidewall curving along the arc of a circle of a radius of125/8 in. from a taper of 5° 30' at the rim, and an O.D. over the rim of3.155 inches. The stacking distance or height between the bottoms oflike cups in a nested relationship was 0.390 inch. Each such cup had avolumetric capacity to overflowing of 9 fl. oz. and such cups were foundto be very well suited, in rigidity, liquid impermeability andinsulating properties for hot beverages such as coffee. Cups of similardesign have also been satisfactorily constructed from expandedpolystyrene sheets of the following thicknesses and densities: 1) 18 lb.per cu. ft. and 25 mil, 2) 10 lb. per cu. ft. and 30 mil, 3) 15 lb. percu. ft. and 20 mil and 4) 18 lb. per cu. ft. and 25 mil.

But for some differential post-expansion of the foam sheet which isapparently caused by differential application of heat thereto and whichled to some increase in density in the sidewall of the cup in the regionof the rim, the density of the cup sidewall remained relatively uniformthroughout. As a result, it could be fairly said that the product ofsidewall circumference at any elevation and thickness at that elevationremained relatively constant through a major portion of the cup.

The invention, and an operative embodiment thereof, has been describedabove in terms sufficiently full, clear, concise and exact as to enableany person skilled in the art to make and use the same. It is to beunderstood, however, that it is within our contemplation that certainmodifications of the above-described mode of practicing the inventioncan be made by a skilled artisan without departing from the scope of theinvention and it is, therefore, desired to limit the invention only inaccordance with the appended claims.

We claim:
 1. A nestable cup-like container comprising, in combination: asidewall formed by heat shrinking a sleeve formed from a singledouble-ended sheet of a heat-shrinkable thermoplastic material, andhaving an inner surface adapted to contact a liquid product to becontained in said container, the ends of said sheet being joined to oneanother to form a liquid-tight seam extending from the top to the bottomof said container, said container having a mouth at its top which isdefined by the upper portion of the sidewall, said sidewall continuouslyand progressively tapering inwardly and downwardly from a point near theopen mouth of the container to a point near the bottom of the containerfor a major portion of the height of the container, the height of saidmajor portion constituting substantially more than one-half of saidcontainer, the thickness of the sidewall increasing continuously andprogressively over said major portion from a lesser thickness at the topto a greater thickness at the bottom thereof as a result of the heatshrinking of the sleeve; and means joined to the sidewall for closingthe bottom of the container in a liquid-tight manner.
 2. A containeraccording to claim 1 where said heat-shrinkable thermoplastic materialis an expanded, heat-shrinkable thermoplastic material.
 3. A two-piececontainer according to claim 1 wherein the means for closing the bottomof the container is a piece which is separate from the unitary sidewalland which is sealingly joined thereto.
 4. A container according to claim1 wherein the uppermost portion of the double-ended blank from which thesidewall is formed is reversely folded into a relatively thin, tightbead which surrounds the mouth of the container.
 5. A containeraccording to claim 2 wherein said expanded heat-shrinkable thermoplasticmaterial comprises polystyrene of an average density of the order of 10to 18 pounds per cubic foot.
 6. A container in accordance with claim 5wherein the thickness of the sidewall of such container, at an elevationproximate to the upper open end thereof, is of the order of 20-30 mils.7. A container according to claim 2 wherein the taper of the majorportion of the sidewall increases from a minimum taper at an upper,thinner region of said major portion to a greater taper at a lower,thicker region thereof.
 8. A container according to claim 7 wherein saidtaper is of the order of 5°-7° at the upper region of the major portionof the sidewall and is of the order of at least 15° at the lower regionthereof.
 9. A container according to claim 7 wherein said taperincreases progressively from said minimum taper to said greater taperalong the distance from said upper region to said lower region.
 10. Acontainer according to claim 1 wherein the sidewall is provided with aninwardly extending shoulder at a location outside of said major portionagainst which a portion of a substantially identical container isadapted to abut when said substantially identical container is insertedinto said container in nested relationship to maintain a predeterminedminimum spacing between said containers.
 11. A pair of substantiallyidentical containers each of which is constructed in accordance withclaim 10, one of said containers being inserted in the other in nestedrelationship with said portion of said container abutting against thesaid shoulder of the other container.
 12. A container according to claim10 wherein said inwardly extending shoulder is located in said sidewallat a location below said major portion, and wherein the portion of asubstantially identical container is an annular portion of the bottomthereof.
 13. A pair of substantially identical containers each of whichis constructed in accordance with claim 12, one of said containers beinginserted in the other in nested relationship with said annular portionof the bottom of said container abutting against the said shoulder ofthe other container.
 14. A container according to claim 2 wherein theends of the sheet of thermoplastic material are joined to one another inan overlapped relationship, and wherein the sidewall is of a reducedthickness and increased density in the region of the overlapping ends.15. The combination comprising a container according to claim 1 and aliquid container therein, said liquid being in face to face contact withthe inner surface of the sidewall of the container.
 16. The combinationaccording to claim 15 wherein the heat-shrinkable thermoplastic materialis an expanded, heat-shrinkable thermoplastic material and wherein theliquid is a hot beverage.
 17. A one-piece nestable cup-like containercomprising, in combination: a sidewall formed by heat-shrinking a sleeveformed from a single double-ended sheet of a heat-shrinkablethermoplastic material, and having an inner surface adapted to contact aliquid product to be contained in said container, the ends of said sheetbeing joined to one another to form a liquid-tight seam extending fromthe top to the bottom of said container, said container having a mouthat its top which is defined by the upper portion of the sidewall, saidsidewall continuously and progressively tapering inwardly and downwardlyfrom a point near the open mouth of the container to a point near thebottom of the container for a major portion of the height of thecontainer, the height of said major portion constituting substantiallymore than one-half of said container, the thickness of the sidewallincreasing continuously and progressively over said major portion from alesser thickness at the top to a greater thickness at the bottom thereofas a result of the heat shrinking of the sleeve; and means closing thebottom of the container which means comprises an inwardly foldedlowermost integral portion of the double-ended sheet from which thesidewall is formed.